Swift class "does not implement (objc) protocol"

Question

I'm having trouble making a Swift NSManagedObject subclass conform to an Objective-C protocol.

I've created a model protocol in order to abstract somewhat my Core Data models from other components in my app which have no business knowing these things are Core Data Managed Objects...

So I have a protocol as follows:

@protocol UserProtocol <NSObject>

@property (nonatomic) NSSet *friends;

@end

And my managed object subclass in swift is:

class User: NSManagedObject, UserProtocol {

    @NSManaged var friends: Set<User>

}

Unfortunately I am being told User does not conform to UserProtocol. I can't find a way to see the swift interpretation of my Objective-C protocol, is there a way to do that? If I can see that I could work out why my swift class isn't matching the protocol.

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Perhaps you need getters and setters? Also, is var Set not equivalent to NSMutableSet? — Mundi
– Mundi, Commented Jun 30, 2015 at 11:16
@NSManaged requires var. You've got a point though maybe Set resolves to NSMutableSet. So isn't there a way to get a Swift view on an Objective-C piece of code? — Daniel
– Daniel, Commented Jun 30, 2015 at 11:22
Which Xcode version are you using? In Swift 1.2 (Xcode 6.3.2) NSSet is mapped to Set<NSObject>, so you would have to define the property as @NSManaged var friends: Set<NSObject> to satisfy the protocol. — Martin R
– Martin R, Commented Jun 30, 2015 at 11:31
Thank you, that did fix it. I guess this will all be a lot nicer to work with in Swift 2.0 with Objective-C generics. Please answer the question and I can accept it. — Daniel
– Daniel, Commented Jun 30, 2015 at 12:03

Martin R · Accepted Answer · 2015-06-30 12:37:46Z

1

In Swift 1.2 (Xcode 6.3.2) NSSet is mapped to Set<NSObject>, so you would have to define the property as

@NSManaged var friends: Set<NSObject>

to satisfy the protocol. In Swift 2 you can define the Objective-C protocol method using "lightweight generics".

answered Jun 30, 2015 at 12:37

Martin R

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